This invention relates to a contact probe arrangement for electrically connecting a test system with the circular contact pads of a device to be tested. In order to achieve a low contact resistance the contact probes are orthogonally pressed onto the contact pads, and for adjusting height differences in the contact pads caused by an uneven surface of the device to be tested they may bend out laterally.
Contact probes of this type may be used, for example, for detecting opens and shorts in electrical circuit arrays of microelectronic compounds.
The electrical testing of microelectronic compounds such as printed circuit cards, ceramic modules or semiconductor chips is currently performed mainly with needle cards. In addition to their low durability and frequent need for re-adjustment, the main limitation in the use of needle cards is the minimal distance between two adjacent needles: the distance is around 100 xcexcm in the most favourable case.
An alternative is provided by testing and power supply devices with bending wires. Their principal characteristic is the individual, meandering guiding of each wire in a stack of guide plates. The guide grooves traverse each guide plate orthogonal to its surface. The particular advantage of this technique arises from the possibility of being able to produce relatively dense two-dimensional arrangements of contact wires. In this bending wire technique through-holes must be drilled through the guide plates with a diameter at least as large as the diameter of the contact probe. The distance between the holes is limited by the drilling technique itself, because the wall thicknesses between the holes cannot fall below certain minimums.
A contact probe arrangement of this kind is known from European Patent document EP-A-0 283 545 by T. Bayer et al. and assigned to the assignee herein. This document describes how, despite a reduced diameter of the contact probes, the necessary low contact resistance can be maintained by appropriate arrangement and design in the stack of perforated plates.
U.S. Pat. No. 5,385,477 describes a bending wire contacting device in which the bending wires are encapsulated in a housing filled with dielectric elastic materials, and are thus elastically coupled together. This permits a more dense arrangement of the wires while still ensuring that the individual wires are insulated from each other.
The advantage of the bending wire arrangements described is the possibility of being able to produce relatively dense two-dimensional or flat contact probe arrangements. Numerous test applications in microelectronics specify only dense one-dimensional or linear contact probe arrangements.
The object of the invention is to provide an easy-to-produce, low-cost contact probe arrangement with a very dense linear and flat arrangement.
In the contact probe arrangement in accordance with the invention, the contact probes pressed orthogonally onto the contact pads are located in guide grooves which run parallel to the surface of the guide plate and are covered by a protective plate. The contact probes bend laterally into the areas provided, which likewise run parallel to the surface of the guide plate and are covered by the protective plate.
The guide plates in a plane of a guide plate and the areas for lateral bending can be arranged much more densely next to each other in one plane than is possible in the various stacked planes. The walls between the individual guide grooves and the areas for lateral bending can be much thinner than when through-holes with the diameter of the guide grooves have to be drilled through several guide plates.
As well as a generally more dense arrangement of the contact wires, a very dense one-dimensional arrangement of the contact probes can in particular be achieved in a low-cost way by this means.
An advantageous feature is that the guide grooves and the areas for lateral bending are produced by means of etching techniques. This permits very precise production of the structures, but also with these methods their geometry can be chosen such that lower friction occurs in the guide grooves and the areas for lateral bending. This substantially improves the durability of the contact probe arrangement.